UMD Theses and Dissertations
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Item Stepping into the Breach: Followers Reclaiming Leadership from Formal Leaders(2023) Butler, Alexander I; Hanges, Paul; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recently, DeRue (2011) reconceptualized leadership as a dynamic process in which individuals engage in interdependent and interlocking acts of leading and following called “double interacts.” The behaviors that take place in double interacts are categorized as claims and grants, and they signify the assertion or bestowment of status as leader or follower in interpersonal exchanges. The present study (N = 367) builds upon DeRue’s theoretical model by testing antecedents to claiming and granting. Results show that leader behavior predicts followers’ decisions to claim or grant leader status. Furthermore, followers’ trust perceptions mediate the relationship between leader behavior and claiming and granting, and leader identity magnitude moderates the mediating effect of trust. This study has implications for understanding leader influence, claiming and granting, trust, and leader identity construction.Item Stable Science and Fickle Bodies: An Examination of Trust and the Construction of Expertise on r/SkincareAddiction(2023) DeCusatis, Cara Maria; Sauter, M.R.; Library & Information Services; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)While there is considerable research on the topic of trust when it comes to health information or news media, there is less work examining how trust and expertise are conceptualized for information that may straddle both subjective and objective approaches to knowledge. In this thesis, I use the subreddit r/SkincareAddiction as a field site to examine how users construct skincare expertise and position skincare expertise in relation to formalized bioscience and experiential knowledge. Building on Science and Technology Studies’ theories of lay expertise and embodiment, I investigate how users interpret, share, and enact skincare and subreddit competence, discern trustworthy information, and negotiate the boundaries of science. Through a grounded theory analysis of subreddit posts and comments, I argue that r/SkincareAddiction users engage in forms of boundary work to preserve the expertise of medical professionals and the perceived infallibility of science. I argue that such delineations both uphold formalized systems of expertise and make space for alternative, community-specific forms of skincare expertise. This community-specific expertise is reified through community norms and agreed upon beliefs, such as the understanding that “your mileage may vary” and “everyone’s skin is different”. I situate these community beliefs within feminist understandings of embodied knowledge and argue that these beliefs are what afford users participation in “expert” conversations from which they might otherwise be excluded.Item DOES PATIENT-CENTERED COMMUNICATION AND TRUST IN PHYSICIAN INFORMATION VARY BY CANCER SURVIVORSHIP STATUS? AN ANALYSIS OF THE HEALTH INFORMATION NATIONAL TRENDS SURVEY (HINTS) 2017(2019) Al-Nassir, Marwa Fawzi; Dallal, Cher M; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Trust is the foundation of the patient-physician relationship. Patients’ trust in a physician has been associated with patient satisfaction, adherence to treatment, continuity of care, and improved health outcomes. Trust in a physician is especially important for health-vulnerable populations, such as cancer survivors, as they tend to endure complex emotional needs related to re-acclimating to the new normal post cancer diagnosis. The patient-physician relationship also relies heavily on effective patient-centered communication (PCC), however, associations between PCC and trust in physician information overall and by cancer survivorship status is not well understood. Using nationally representative data (N = 2604) ascertained from Cycle 1 of the fifth iteration of the 2017 Health Information National Trends Survey (HINTS), a cross-sectional analysis was conducted to examine PCC in relation to trust in physician information. PCC was assessed on a 4-point Likert scale using responses from seven sub-questions that address the main functions of PCC: 1) fostering healing relationships, 2) exchanging clinical information, 3) responding to emotional needs, 4) managing uncertainty, 5) facilitating shared decision-making, and 6) enabling patient self-management. Trust in physician information was analyzed dichotomously (high versus low) based on responses from a single item question. PCC was analyzed as individual components (optimal versus sub-optimal) and as an overall score. Confounders included age, sex, race/ethnicity, education, and household annual income. Odds ratios (OR) and 95% confidence intervals (CI) for the relationship between PCC and trust in physician information were estimated using multivariable logistic regression. Analyses of cancer survivorship status (cancer survivor versus never had cancer) as an effect modifier of the relationship between PCC and trust in physician information was also conducted using an interaction term. Results from the weighted multivariable models revealed that for every one-unit increase in the overall PCC score (range 1 to 100), the odds of having high trust in physician information increased by 4% (adj OR = 1.04, 95% CI = 1.03–1.05). The odds of reporting high level of trust in physician information were significantly associated with each individual component of PCC when comparing those who felt their communication component was optimal versus sub-optimal (PCC components: exchanging clinical information (adj OR = 2.57, 95% CI = 1.82–3.62), responding to emotional needs (adj OR = 2.34, 95% CI = 1.65–3.30), facilitating in shared decision-making (adj OR = 2.35, 95% CI = 1.70–3.26), enabling patient self-management (adj OR = 2.88, 95% CI = 2.11–3.92), managing uncertainty (adj OR = 2.45, 95% CI = 1.74–3.44), fostering healing relationships (adj OR = 2.79, 95% CI = 2.18–3.57), and spending enough time with you (adj OR = 2.09, 95% CI = 1.49–2.93)). When examining relationships by cancer survivorship status, estimates among cancer survivors were of greater magnitude compared to persons who reported never having cancer, however, no significant interactions were observed in the weighted multivariable models (all p-interaction>0.05). These findings provide insight on how optimal experiences of PCC influence trust in physician information and can help inform the development of PCC strategies to ultimately improve health outcomes and reduce consequences related to poor patient-physician trust overall and among cancer survivors.Item Security and Energy Efficiency in Resource-Constrained Wireless Multi-hop Networks(2016) Paraskevas, Evripidis; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In recent decades, there has been a huge improvement and interest from the research community in wireless multi-hop networks. Such networks have widespread applications in civil, commercial and military applications. Paradigms of this type of networks that are critical for many aspects of human lives are mobile ad-hoc networks, sensor networks, which are used for monitoring buildings and large agricultural areas, and vehicular networks with applications in traffic monitoring and regulation. Internet of Things (IoT) is also envisioned as a multi-hop network consisting of small interconnected devices, called ``things", such as smart meters, smart traffic lights, thermostats etc. Wireless multi-hop networks suffer from resource constraints, because all the devices have limited battery, computational power and memory. Battery level of these devices should be preserved in order to ensure reliability and communication across the network. In addition, these devices are not a priori designed to defend against sophisticated adversaries, which may be deployed across the network in order to disrupt network operation. In addition, the distributed nature of this type of networks introduces another limitation to protocol performance in the presence of adversaries. Hence, the inherit nature of this type of networks poses severe limitations on designing and optimizing protocols and network operations. In this dissertation, we focus on proposing novel techniques for designing more resilient protocols to attackers and more energy efficient protocols. In the first part of the dissertation, we investigate the scenario of multiple adversaries deployed across the network, which reduce significantly the network performance. We adopt a component-based and a cross-layer view of network protocols to make protocols secure and resilient to attacks and to utilize our techniques across existing network protocols. We use the notion of trust between network entities to propose lightweight defense mechanisms, which also satisfy performance requirements. Using cryptographic primitives in our network scenario can introduce significant computational overhead. In addition, behavioral aspects of entities are not captured by cryptographic primitives. Hence, trust metrics provide an efficient security metric in these scenarios, which can be utilized to introduce lightweight defense mechanisms applicable to deployed network protocols. In the second part of the dissertation, we focus on energy efficiency considerations in this type of networks. Our motivation for this work is to extend network lifetime, but at the same time maintain critical performance requirements. We propose a distributed sleep management framework for heterogeneous machine-to-machine networks and two novel energy efficient metrics. This framework and the routing metrics are integrated into existing routing protocols for machine-to-machine networks. We demonstrate the efficiency of our approach in terms of increasing network lifetime and maintaining packet delivery ratio. Furthermore, we propose a novel multi-metric energy efficient routing protocol for dynamic networks (i.e. mobile ad-hoc networks) and illustrate its performance in terms of network lifetime. Finally, we investigate the energy-aware sensor coverage problem and we propose a novel game theoretic approach to capture the tradeoff between sensor coverage efficiency and energy consumption.Item Security and Trust in Mobile Ad-Hoc Networks(2015) Jain, Shalabh; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Distributed ad-hoc networks have become ubiquitous in the current technological framework. Such networks have widespread applications in commercial, civil and military domains. Systems utilizing these networks are deployed in scenarios influencing critical aspects of human lives, e.g.: vehicular networks for road safety, infrastructure monitoring for smart grid or wildlife, and healthcare systems. The pervasive nature of such systems has made them a valuable target for adversarial action. The risk is compounded by the fact that typically the networks are composed of low power, unattended devices with limited protection and processing capabilities. Usage of cryptographic primitives can prove to be a significant overhead in these scenarios. Further, behavioral aspects of participants, that are critical for distributed system operation, are not effectively addressed by cryptography. In this dissertation, we explore the direction of using notions of trust and privacy to address security in these networks. In the first part of the dissertation, we consider the problems of generation, distribution and utilization of trust metrics. We adopt a cross-layer and component based view of the network protocols. We propose schemes operating at the physical layer of the communication stack, to generate trust metrics. We demonstrate that these schemes reliably detect relay adversaries in networks, and can be an effective measure of trust for the neighborhood discovery component. We propose techniques to combine trust from different detectors across multiple layers into a singular trust metric. Further, we illustrate via simulations, the advantages and disadvantages of existing techniques for propagation of local trust metrics throughout the network. We propose modifications to increase the robustness of the semiring based framework for trust propagation. Finally, we consider utilization of trust metrics to increase resilience of network protocols. We propose a distributed trust based framework, to secure routing protocols such as AODV, DSR. We highlight utility of our framework by using the proposed point-to-point link trust metrics. In the second part of the dissertation, we focus on the role of privacy in ad-hoc networks. We demonstrate that for three broad categories of systems; distributed state estimation, distributed consensus and distributed monitoring systems, privacy of context can reduce cryptographic requirements (such as the need for encryption). In fact, efficient methods to preserve privacy can significantly reduce the energy footprint of the overall security component. We define a privacy framework applicable to these scenarios, where the network can be partitioned into a hierarchical structure of critical and non-critical components. We utilize a physical layer watermarking scheme to ensure privacy guarantees in our framework. Further, for systems that lack a natural hierarchical structure, such as information fusion systems, we define an efficient framework to define a hierarchy (network partition), without leaking the structure to the adversary.Item TRUST-BASED DEFENSE AGAINST INSIDER PACKET DROP ATTACKS IN WIRELESS SENSOR NETWORKS(2013) Cho, Youngho; Qu, Gang; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In most wireless sensor networks (WSNs), sensor nodes generate data packets and send them to the base station (BS) by multi-hop routing paths because of their limited energy and transmission range. The insider packet drop attacks refer to a set of attacks where compromised nodes intentionally drop packets. It is challenging to accurately detect such attacks because packets may also be dropped due to collision, congestion, or other network problems. Trust mechanism is a promising approach to identify inside packet drop attackers. In such an approach, each node will monitor its neighbor's packet forwarding behavior and use this observation to measure the trustworthiness of its neighbors. Once a neighbor's trust value falls below a threshold, it will be considered as an attacker by the monitoring node and excluded from the routing paths so further damage to the network will not be made. In this dissertation, we analyze the limitation of the state-of-the-art trust mechanisms and propose several enhancement techniques to better defend against insider packet drop attacks in WSNs. First, we observe that inside attackers can easily defeat the current trust mechanisms and even if they are caught, normally a lot of damage has already been made to the network. We believe this is caused by current trust models' inefficiency in distinguishing attacking behaviors and normal network transmission failures. We demonstrate that the phenomenon of consecutive packet drops is one fundamental difference between attackers and good sensor nodes and build a hybrid trust model based on it to improve the detection speed and accuracy of current trust models. Second, trust mechanisms give false alarms when they mis-categorize good nodes as attackers. Aggressive mechanisms like our hybrid approach designed to catch attackers as early as possible normally have high false alarm rate. Removing these nodes from routing paths may significantly reduce the performance of the network. We propose a novel false alarm detection and recovery mechanism that can recover the falsely detected good nodes. Next, we show that more intelligent packet drop attackers can launch advanced attacks without being detected by introducing a selective forwarding-based denial-of-service attack that drops only packets from specific victim nodes. We develop effective detection and prevention methods against such attack. We have implemented all the methods we have proposed and conducted extensive simulations with the OPNET network simulator to validate their effectiveness.Item Getting on the Same Page: How Leaders Build Trust Consensus in Teams and Its Consequences(2012) Fulmer, C. Ashley; Ostroff, Cheri; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Existing organizational research has demonstrated that team members' trust in leaders is positively related to a team's bottom-line outcomes. However, little is known about how collective trust in leaders develops among team members. To address this gap, the present study examines the effects of multiple emergent processes on the extent to which team members exhibit consensus in trust in their leader. In particular, it was proposed that the most important factors for the emergence, and the degree of consensus, of collective trust in leaders should have the same referent target as the collective construct (i.e., the leader) and concern behaviors that involve interactions between the leader and team members. Thus, the leader behavior and interactions variables of showing concern, leading by example, and monitoring were expected to exert stronger influence on the consensus in trust in leaders than leader attributes (ability and integrity) and team factors (open communication and demographic diversity). Further, the degree of consensus in trust in leaders was predicted to have both an independent and interaction effect with the mean level of trust in leaders in influencing team performance and voice behavior. Three waves of survey data were collected from teams with new leadership in a large academic military institution. Data from 719 team members from 105 teams were used to test these predictions by analyzing consensus concurrently and changes in consensus over time. The results generally supported the relative importance of leader showing concern and leading by example on the degree of consensus in trust in leaders in the concurrent model. For changes in consensus, leading by example was particularly important. In addition, while consensus was not independently related to the team performance and voice behaviors, it interacted with the mean level in influencing the outcomes in both the concurrent and change models. Taken together, the findings suggest that some leader behaviors are important for the development of collective trust or consensus in trust in leaders, and further suggest that consensus can act as a boundary condition for the effect of the mean level of trust in leaders on team outcomes. By focusing on the consensus in trust in leaders, this research begins to shed light on how consensus in trust develops among team members with respect to their leader and has implications for understanding trust, leadership, and emergence.Item Dynamic Trust Processes after Violation: Trust Dissolution and Restoration(2010) Fulmer, C. Ashley; Gelfand, Michele; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Trust and violation go hand in hand in our everyday life. However, few studies have directly examined the effects of violation on trust and delineated the nonlinear patterns of trust changes after violation. In this research, I focused on trust dynamics in two phases after violation: trust dissolution and trust restoration. Specifically, I examined how the individual differences of collectivistic self-construal and group identification, in conjunction with the situational variables of violation magnitude and trustee's group membership (ingroup vs. outgroup), moderate the relationship between trust violation and changes in trust level and trajectory across the two phases. The study adopted an economic game methodology--the Investment Game (Berg, Dickhaut, & McCabe, 1995)--that allows repeated measures of trust. Results from discontinuous growth modeling indicated that the trust changes after violation, in dissolution and restoration, are a function of violation magnitude, collectivistic self-construal, ingroup and outgroup dynamics, and group identification. Further, the dynamic patterns revealed a black sheep effect. Individuals high on collectivistic self-construal and group identification exhibited a larger and faster trust decrease during dissolution and a slower increase during restoration after a large than a small ingroup violation. High collectivists high on group identification also showed slower trust restoration after a large ingroup violation than high collectivists low on group identification. However, the black sheep effect was absent when collectivists experienced an outgroup violation or were low on group identification. Implications for future research and intercultural relations are discussed.Item Robust Trust Establishment in Decentralized Networks(2010) Seng, Chuk-Yang; Arbaugh, William; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The advancement in networking technologies creates new opportunities for computer users to communicate and interact with one another. Very often, these interacting parties are strangers. A relevant concern for a user is whether to trust the other party in an interaction, especially if there are risks associated with the interaction. Reputation systems are proposed as a method to establish trust among strangers. In a reputation system, a user who exhibits good behavior continuously can build a good reputation. On the other hand, a user who exhibits malicious behavior will have a poor reputation. Trust can then be established based on the reputation ratings of a user. While many research efforts have demonstrated the effectiveness of reputation systems in various situations, the security of reputation systems is not well understood within the research community. In the context of trust establishment, the goal of an adversary is to gain trust. An adversary can appear to be trustworthy within a reputation system if the adversary has a good reputation. Unfortunately, there are plenty of methods that an adversary can use to achieve a good reputation. To make things worse, there may be ways for an attacker to gain an advantage that may not be known yet. As a result, understanding an adversary is a challenging problem. The difficulty of this problem can be witnessed by how researchers attempt to prove the security of their reputation systems. Most prove security by using simulations to demonstrate that their solutions are resilient to specific attacks. Unfortunately, they do not justify their choices of the attack scenarios, and more importantly, they do not demonstrate that their choices are sufficient to claim that their solutions are secure. In this dissertation, I focus on addressing the security of reputation systems in a decentralized Peer-to-Peer (P2P) network. To understand the problem, I define an abstract model for trust establishment. The model consists of several layers. Each layer corresponds to a component of trust establishment. This model serves as a common point of reference for defining security. The model can also be used as a framework for designing and implementing trust establishment methods. The modular design of the model can also allow existing methods to inter-operate. To address the security issues, I first provide the definition of security for trust establishment. Security is defined as a measure of robustness. Using this definition, I provide analytical techniques for examining the robustness of trust establishment methods. In particular, I show that in general, most reputation systems are not robust. The analytical results lead to a better understanding of the capabilities of the adversaries. Based on this understanding, I design a solution that improves the robustness of reputation systems by using accountability. The purpose of accountability is to encourage peers to behave responsibly as well as to provide disincentive for malicious behavior. The effectiveness of the solution is validated by using simulations. While simulations are commonly used by other research efforts to validate their trust establishment methods, their choices of simulation scenarios seem to be chosen in an ad hoc manner. In fact, many of these works do not justify their choices of simulation scenarios, and neither do they show that their choices are adequate. In this dissertation, the simulation scenarios are chosen based on the capabilities of the adversaries. The simulation results show that under certain conditions, accountability can improve the robustness of reputation systems.Item THE ROLE OF TRUST AND CARE IN THE IMPLEMENTATION OF A SOCIAL CONSTRUCTIVIST CURRICULUM IN PHYSICAL EDUCATION(2009) Tolley, Christina Ballard; Ennis, Catherine D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Social constructivism centers on the belief that social interaction is paramount to effective and meaningful learning. This study examined how trusting and caring teacher-student and student-student relationships influenced students' willingness and ability to learn in a social constructivist physical education curriculum. Data were collected through student interviews and focus groups, observations (teacher log), student member checks, and independent observations. Data were analyzed using open, axial, and selective coding consistent with the ethnographic research design. The findings suggested that students' willingness and ability to learn were positively influenced through the implementation of the social constructivist curriculum Teaching Games for Understanding (TGfU). Specifically, this was achieved through the classroom environment that facilitated students' perceptions of a trusting and caring teacher, contributing to more open and honest student relationships. These factors could be interpreted as an integrated spiral that contributed to teacher and student trust and care.